Musical instrument having automatic arpeggio circuitry

ABSTRACT

A musical instrument having a keyboard is provided with means for playing or producing an arpeggio automatically. Key switches under the control of the left-hand portion of the keyboard determine which tone producing means normally under the control of the right-hand portion of the keyboard shall be automatically actuated in sequence in the style of an arpeggio. A selectively actuatable switch is used to initiate the arpeggio and controls a triggerable circuit that provides a ramp potential for sequentially energizing the various stages of a cascade circuit that produces a series of control pulses sequentially which are directed to momentarily energize or actuate the tone producing means to make up the arpeggio.

United States Patent [72] Inventor Alberto E. Kniepkamp Chicago, Ill.

[211 App]. No. 41,149

[22] Filed May 25, 1970 [45] Patented Nov. 2, 1971 [73] Assignee Chicago Musical Instrument Co.

Lincolnwood, Ill.

[54] MUSICAL INSTRUMENT HAVING AUTOMATIC ARPEGGIO CIRCUITRY 26 Claims, 5 Drawing Figs.

[52] U.S. Cl 84/l.l7, 84/1 .24, 84/DIG. 22 [51] lnt.Cl Gl0h 1/02 [50] Field of Search 84/ 1.01,

1.17, 1.24, DIG. 4, 22, 23

[56] References Cited UNITED STATES PATENTS 8/1965 Von Gunten 84/l.l7 X

3,227,027 1/1966 VonGunten 3,358,070 12/1967 Young ABSTRACT: A musical instrument having a keyboard is provided with means for playing or producing an arpeggio automatically. Key switches under the control of the left-hand portion of the keyboard determine which tone producing means normally under the control of the right-hand portion of the keyboard shall be automatically actuated in sequence in the style of an arpeggio. A selectively actuatable switch is used to initiate the arpeggio and controls a triggerable circuit that provides a ramp potential for sequentially energizing the various stages of a cascade circuit that produces a series of control pulses sequentially which are directed to momentarily energize or actuate the tone producing means to make up the arpeggio.

5 J 7 H20 yous) PATENTEBNBV 2 ml 3,617,602

SHEET 2 [IF 3 AMP MUSICAL INSTRUMENT HAVING AUTOMATIC ARPEGGIO CIRCUITRY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to musical instruments, and more specifically to means for producing an arpeggio automatically.

2. Prior Art It has been common for skilled musicians to play a keyboard instrument with at least a melody played by the right hand and chord type of accompaniment played by the left hand, and while holding the chord accompaniment, to play an ascending series of notes corresponding musically to the accompaniment as a type of flourish, dressing or embellishment, whether written into the selection being played or not.

Stinson et aL in a device commercialized under the trademark VIRTUOSO and Young in U.S. Pat. No. 3,358,070 have employed an auxiliary keyboard for manual playing of arpeggios comprising tones determined by key switches associated with the left-hand portion of the keyboard. These structures have the disadvantage that use of the auxiliary keyboard requires either the detachment of the hand from the righthand portion that was being played so.that the hand at that time cannot perform its usual playing functions or is somewhat restricted in doing so. Further, and this is an important point for unskilled musicians, the detachment of the hand for arpeggio use necessitates that the musician redetermine where the hand should be placed to resume the conventional playing of the right-hand portion of the keyboard.

SUMMARY OF THE INVENTION According to my invention, a musical instrument is provided with a series of control gates that are tentatively energized or selected in response to the depressing of keys of the left-hand portion of the keyboard, a selectably actuatable arpeggio switch, and means responsive to actuation of such switch for successively automatically applying spaced pulses of gating potential to such gates.

Accordingly, it is an object of the present invention to provide a musical instrument with means for selectably producing an arpeggio automatically during normal playing of the instrument.

A further object of the present invention is to provide an automatic arpeggio device wherein the arpeggio is initiated during playing of the instrument without the necessity for lifting either hand from the keyboard.

Another object of the present invention is to provide an automatic arpeggio feature which can be added to existing instruments.

Many other advantages, features and additional objectives of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

ON THE DRAWINGS FIGS. 1, 2, 3 and 4 are portions of a circuit diagram that are related to each other as shown diagrammatically in FIG. 5, illustrating representative portions of a musical instrument having an automatic arpeggio means provided in accordance with the principles of the present invention.

AS SHOWN ON THE DRAWINGS The principles of the present invention are particularly useful when embodied in a musical instrument such as illustrated in part in FIG. 2, generally indicated by the numeral 10. In the present instance, the instrument can be considered as being an organ, but the principles are equally applicable to other keyboard instruments such as pianos. The instrument 10 has a conventional keyboard with a left-hand portion and a righthand portion. The left-hand portion may be the lower manual of a 2-manual instrument, the left part of a single manual instrument, or a chord-button section of an instrument that has a further manual. The automatic arpeggio means of this invention may thus be a factory-installed feature of the instrument or it can be constructed as an accessory to be added to otherwise complete musical instruments.

In the illustrated example, the instrument 10 has a series of tone producing means, one of which is illustrated at 11 which can be of any known type. Such means can also represent various points in a formant circuit. The series of tone producing means are able to provide tones or signals that have fundamental frequencies which are related to each other in the manner of the frequencies of a chromatic musical scale. Each tone producing means 11 in this embodiment is controlled by a keyer circuit 12 which is connected to a collector bus 13 which leads to an electronic amplifier 14, the output of which is directed to one or more speakers 15. The instrument 10 has a keyboard with right and left-hand portions, the right-hand portion including a conventional series of keys such as 16 each connected to operate a key switch 17 that is connected to the keyer circuit 12 associated with the corresponding tone producing means 11. A keying potential such as 20 volts DC is applied to a bus 18 which is common to all of the key switches 17. Thus, when the key 16 is depressed, the key switch I7 is closed and is provided with a keying potential whereby a corresponding tone appears at the speaker 15. For each of the other keys 16, there is provided a corresponding key switch and a corresponding tone signal source connected to a keyer circuit, and all such keyer circuits for the other tone signal sources are connected to the collector bus 13.

The automatic arpeggio means herein disclosed include an arpeggio switch 19 connected to a source of potential and having a normally open contact 20 connected to the input of a triggerable circuit generally indicated at 21. The triggerable circuit 21 has a point or output terminal 22 that is coupled to a current amplifier 23 which is coupled to the input of a cascade circuit 24. The arpeggio switch 19 has a normally closed terminal 25 which is the input of a reset circuit 26 which is coupled to the point or output 22 of the triggerable circuit 21. The cascade circuit 24 has a number of stages 27 which as a group are progressively responsive to a potential increase that is applied to the input of the cascade circuit 24. The various stages 27 are each provided with a connection 28, and the connections 28 respectively lead to a series of control gates 29 that are arranged in groups corresponding to chromatically adjacent musical tones, each of which is identified adjacent to the respective control gates 29. A keying potential such as 20 volts is applied to a keying bus 30 (FIG. 4) which may be a part of the keying bus 18. In association with the bus 30, there are a number of key-actuated switches associated with the left-hand portion of the keyboard, these key switches each including a movable contact 31 that is engageable with the bus 30 for receiving the keying potential. The octavely related key switch elements 31 are connected together, and are connected through a line 32 to that one or ones of the series of control gates 29 which correspond to the same musical note, the octavely related control gates 29 being also connected together. There are 12 lines 32 which thus are respectively associated with each of the 12 musical notes of a chromatic octave. A diode 33 forms part of the connection between the various lines 32 and the various control gates 29. The diode 33 serves to protect the associated control gate 29 against possible reverse breakdown.

Each of the control gates 29 comprises a transistor of the PNP-type which is conductive when its base is more negative than its emitter. The base of each control gate 29 is connected through a resistor 34 to one of the connecting lines 28, and in this embodiment, three such bases associated with chromatically adjacent tone producing means have their resistors 34 connected as a group to one of the lines 28. The keying potential at the bus 18 is connected by a line 35 to a common point or line 36 in the cascade circuit 24 and thence through a further resistor 37 of high impedance to the various connecting lines 28, so that the base of each of the series of control gates 29 is positively biased. The emitter of each control gate 29 is normally floating, but when the key switch 31 associated therewith is actuated, the same keying potential appears on the emitter. When the key switch 17 is actuated, again the same keying potential appears but on the collector. Thus, during normal play, the base is biased to keying potential and either or both of the collector and the emitter are biased to the same potential so that during normal playing each of the control gates is nonconductive.

Keying of one of the keys in the left-hand portion of the keyboard will produce the customary effects in a musical instrument by virtue of means omitted from this drawing. In addition, the key switch 31 will close, bringing keying potential to the emitter of all of the control gates 29 of the same basic musical note. However, each of the control gates 29 blocks that keying potential so that it cannot pass through its collector line 38 to the associated keyer circuit 12. (For simplicity of illustration, the various collector lines 38 have been broken off except for the uppermost note, it being understood that each of the other collector lines is associated with similar conventional circuitry of the musical instrument.) However, it can be seen that if the base of the control gate were to become more negative than the applied keying potential on the emitter, the control gate would be conductive. Thus, where the voltage variation on the base is in the form of a pulse, the control gate 29 would be conductive for the duration of the pulse. As explained below, the connecting lines 28 provide such pulses. The first pulse to occur passes through the left connecting line 28 and appears on the bases of the control gates associated with the tones F3,F #3, and G3. The second pulse comes on the next line 28 and is directed to the control gates 29 associated with the tonesG#3,A3 andA#3.The third pulse thus appears on the bases associated with the tone producing means B3, C4 andC#4. This sequence continues so that each of the groups of control gates is successively provided with time-spaced pulses. Then, depending upon what keys are depressed in the left-hand portion of the keyboard, corresponding tone producing means are momentarily energized to provide the arpeggio. Where a chord is played that has considerable spacing between two of the chord notes, there is a possibility that a given pulse from the cascade circuit 24 would not render any control gate 29 to be conductive. This would produce an awkward instant of silence whereby an unwanted loping rhythm would be generated or indicated by such moment of silence. To minimize such an eventuality, means are provided that so interconnect pairs of chromatically adjacent groups of control gates that the control gate of one group of one of the pairs of groups, which gate is chromatically the closest to the other group of the pair, will receive the successive gating pulses for both of such groups. To that end, a resistor 39 interconnects the control gate associated with the lowest frequency tone producing means of one group with the adjacent group associated with lower frequency toneproducing means. In this manner, the lowest frequency gate in one group will also receive the gating pulse for the adjacent group.

The triggerable circuit 21 of the FIG. 1 portion of the diagram includes an integrator circuit 40 which is primarily under the control of a normally conducting control transistor 41. The transistor 41 has its emitter connected to a source of potential while its base is grounded through a resistor 42 whereby the potential appears at the collector which is connected to a point 43 in the integrator circuit. The integrator circuit includes an integrating transistor 44 whose emitter is connected to a source of potential and the collector of which is connected to the point 22. The integrator circuit further includes a capacitor 45 connected across the base and the collector of the integrating transistor 44, one side of the capacitor 45 being connected through the point 43, and the other side being connected to the point 22. The source of potential is also connected through a resistor 46 to the base of the integrating transistor 44 and also through a resistor 47 which with a potentiometer 48 serves as a voltage divider having a movable element or wiper connected through a further resistor 49 to the base of the integrating transistor 44 and to one side of the capacitor 45 through the point 43.

The reset circuit 26 includes a gate or reset transistor 50 having a grounded emitter, a collector connected through a resistor 51 to the point 22 and hence both the capacitor 45 and the collector of the integrating transistor 44. The reset transistor 50 has its base connected through a resistor 52 to the arpeggio switch 19, the base being referenced with respect to ground by a resistor 53. The reset transistor 50 normally has a potential applied 'to its base so that it is conductive and forms part of the charging path for the capacitor 45 which is normally charged. As both of the transistors 41 and 50 are normally biased to conduction, the potential applied to the emitter of the control transistor 41 appears at one side of the capacitor 45 while the other side thereof is grounded through the conductive reset transistor 50. By this arrangement, the point 22 is normally substantially at ground potential while the emitter and the base of the integrating transistor 44 are normally both at the same keying potential, here 20 volts, and thus biased to be nonconductive.

When the arpeggio switch 19 is momentarily actuated, the biasing potential is removed from the reset transistor 50, thus opening a low impedance charging path for the capacitor 45. Further, actuation of the arpeggio switch 19 applies potential to the terminal 20 and hence to the base of the control transistor 41 which is thereby rendered nonconductive since that potential corresponds to the potential on the emitter, thereby further opening at another point the low impedance charging path for the capacitor 45. However, at that instant, the charge of the capacitor 45 will still appear on the base of the integrating transistor 44 and so it will temporarily remain nonconductive. At this point, the capacitor 45 will begin to discharge through a high-impedance path including a further resistor 54 which is grounded and connected to one side of the capacitor 45, and other high impedance means connected between the point 43 and ground which here comprise the re sistor 49 and a portion of the adjustable voltage divider 48. Thus, while the capacitor 45 can be rapidly charged through a low impedance path, it is comparatively slowly discharged through a high-impedance path. Using values given below, the discharge time for the capacitor 45 can be adjusted from a very short time up to about 2 seconds.

When the arpeggio run is to be initiated, and a chord is being played in the left-hand portion of the keyboard, the musician operates the arpeggio switch 19 for one cycle. During the first portion of the cycle, the potential is removed from the reset circuit 26 and applied to the triggerable circuit 21, and after the arpeggio has been completed, the switch 19, which preferably is foot-operated, is released and the second portion of the cycle takes place, namely that the potential is removed from the terminal 20 and applied to the terminal 25. Because of the bias of the resistor 42, the control transistor 41 is immediately rendered conductive, and because of the potential bias on the base of the reset transistor 50, it too is rendered immediately conductive whereby the capacitor 45 is instantly recharged through the low-impedance-charging path. The potential thus also immediately appears at the base of the integrating transistor 44 and restores the initial blocking conditions. If the arpeggio switch 19 is released before the arpeggio has been completed, discharge of the capacitor 45 will be immediately interrupted and recharging will take place so that the next arpeggio again begins with the lowest frequency tone being played.

The reset circuit 26 assures that the capacitor 45 will have a full charge for the next cycle no matter how often the arpeggio switch 19 is cycled.

During discharge of the capacitor 45, the potential that appears at the terminal 22 gradually increases for a period of time corresponding to the discharge time, and that potential increase is linear. As that potential increases linearly and since the duration of such increase is for a very appreciable period of time, that potential is also referred to herein as being a ramp potential. The time involved must always be as long and preferably a little longer than that desired for the arpeggio.

The integrator circuit produces the linear increase in potential as follows. When the control transistor 41 stops conducting in response to actuation of the arpeggio switch, it is out of the circuit for all practical purposes, and at that moment, base current in the integrating transistor 44 will flow. The mag nitude of this current flow will be determined by the voltage present at the wiper of the potentiometer 48 which with the resistor 47 functions as a voltage divider. Thus, the base of the integrating transistor 44 will remain at substantially the same voltage. The resistor 49 provides a path for the base current of the integrating transistor 44 and also for the discharge current of the capacitor 45, the other side of the capacitor 45 being connected to the collector of the integrating transistor 44. Thus, the voltage at point 22 will rise linearly at a rate that is closely proportional to the current passing through the resistor 49.

The progressively increasing ramp voltage is thus coupled from the point 22 to the current amplifier 23 which includes a resistor 55.

The stages 27 of the cascade circuit 24 are progressively responsive to the potential increase of the ramp voltage. Each of the stages 27 includes a capacitor 56, a resistor 57, a pulse gate 58, a resistor 59 and the resistor 37. The resistors 59 are connected together at one end to receive the increasing ramp voltage, and at their other ends respectively to the bases of the various pulse gates 58. The collector of each pulse gate 58 is connected through the resistor 57 to a source of potential that is somewhat higher than the keying voltage, for example 30 volts where the keying voltage is 20. The collector of each pulse gate 58 is also connected to one side of the capacitor 56 while the other side of the capacitor 56 is connected through the resistor 37 to the source of keying potential. Each of the connecting lines 28 is connected to the respective stages at a point between the capacitor 56 and the corresponding resistor 37. The emitter of the pulse gate 58 for each stage is connected to ground in a special manner. The lowermost emitter is connected directly to ground. The next higher emitter is connected to ground through means for providing a potential reference between stages, and such means are provided between the adjacent emitters, all such means being connected in series with each other and jointly comprising a lowimpedance path. In this embodiment, the means that provides a potential reference between successive stages constitutes diode means, here shown as a pair of series-connected diodes 60, 60 connected in series with each other and in series with other pairs of diodes connected between the various emitters.

Each of the capacitors 56 has a high-impedance-charging path that begins with the somewhat higher potential source of 30-volt source, and extends through the resistor 57 to the capacitor 56 and thence through the high-impedance resistor 37 to the source of keying voltage to be completed within the power supply so that in this example, there is a l-volt charge that appears on the capacitor 56. When the capacitor is discharged as explained below, it has a low-impedance discharge path that extends through the collector and the emitter of its pulse gate 58 and thence through any lower diodes 60 to ground.

The successive discharge is effected'as follows. Each of the pulse gate transistors 58 has a typical threshhold value of 0.6 volts. Thus, when the ramp voltage begins to develop, nothing happens until the ramp voltage has built up sufficiently on the base of the lowermost pulse gate transistor 58 to render it conductive, at for instance, 0.6 volts. At that point, a path is provided for the lowermost capacitor 56 to be discharged to ground and during such discharge there is a substantial voltage drop on both sides of the capacitor 56 so that the normal potential of 20 volts provided by the keying potential momentarily drops, and this is sensed as a more negative potential on the lowermost group of control gates 29 which thereby effect their being rendered conductive as previously explained.

In the meantime, the ramp voltage continues to rise at the input to the cascade circuit 24 until the breakdown voltage for the second lowest pulse gate 58 is reached. it, too, has an inherent threshhold voltage of about 0.6 volts, but its emitter is connected through the means for providing a potential reference, to ground. A diode typically also has a threshhold voltage of 0.6 volts, and thus where two such diodes are connected in series between the second emitter and ground, the net effect is that at least 1.8 volts and possibly about 2.0 volts higher potential than that which caused the first breakdown will be needed before the second pulse gate is rendered conductive to discharge its capacitor 56. In like manner, progressively greater ramp potentials are required that increase between 1.8 and 2.0 volts per stage and cause the successively higher pulse gates to become conductive, thereby producing the spaced succession of pulses in the connecting lines 28 that are more negative than the keying voltage. Thus, the various pulse gates are normally nonconducting and each one lies in the low-impedance discharge path for the respective capacitors 56, and when the increasing ramp potential is applied to their control terminal or base, the low-impedance path is thereby gated to enable the rapid discharge of the associated capacitor. Thus, the pulses are derived from the capacitors 56 as they are successively discharged. Thus, the potential reference means 60 or pair of diodes between each stage serves to render the successive pulse gates 58 progressively responsive to increasing control potentials as provided by the linearly increasing ramp potential.

The values given herein assure that the various control gates 29 will be driven to saturation.

The preferred embodiment of the invention has been described with reference to the more common form of arpeggio which entails successively higher notes. By reversal of connections, arpeggios of successively lower notes are produced.

The following are representative sizes for the various capacitors and resistors identified herein:

Although various minor modifications might be suggested by those versed in the art, it is to be understood that I wish to embody within the scope of the patent warranted herein, all such embodiments as reasonably and'properly come within the scope of my contribution to the art.

I claim as my invention:

1. A musical instrument comprising:

a. a series of tone producing means having frequencies corresponding to a chromatic musical scale;

b. a keyboard having a left-hand portion and a right-hand portion, said keyboard including a series of keys connected to respective ones of said tone producing means to control the tone production;

c. a set of key switches under the control of the keys of the left-hand portion of said keyboard connected for providing a keying potential;

d. a series of control gates respectively interconnecting said key switches with musically corresponding ones of the tone producing means associated with the right-hand portion of said keyboard to control tone production independently of the directly associated keys;

e. a selectably actuatable arpeggio switch connected for providing a potential; and

. means responsive to the potential from said arpeggio switch for successively applying spaced pulses of gating potential to said series of control gates.

2. A musical instrument according to claim 1 in which a plurality of octavely related ones of said control gates are connected together to receive keying potential simultaneously from the corresponding key switch.

3. A musical instrument according to claim 2 in which a plurality of octavely related ones of said key switches are connected together.

4. A musical instrument according to claim 1 in which diodes are located in series between said key switches and said control gates.

5. A musical instrument according to claim 1 in which said control gates are arranged in groups each including the control gates for controlling a plurality of chromatically adjacent ones of said tone producing means, the control gates of each group being connected together for receiving one of the pulses of the gating potential.

6. A musical instrument according to claim 5 including means so interconnecting pairs of chromatically adjacent groups of control gates that the control gate of one group of one of the pairs of groups, which gate is chromatically the closest to the other group of the pair, will receive the successive gating pulses for both of such groups.

7. A musical instrument according to claim 5 including means so interconnecting the control gate associated with the lowest frequency tone producing means of one group with the adjacent group associated with lower frequency tone producing means that said control gate will also receive the gating pulse for said adjacent group.

8. A musical instrument according to claim 1 in which said pulse applying means comprises:

a. a circuit, connected to be triggered by each cycle of operation of said arpeggio switch, for providing a potential that increases for a period of time at least as great as the desired arpeggio duration; and

b. a cascade circuit having a series of stages arranged to be progressively responsive to such potential increase to provide said spaced pulses of gating potential.

9. A musical instrument according to claim 8 including means in the triggerable circuit for selectably adjusting said period of time.

10. A musical instrument according to claim 9 in which said adjusting means has a range of about 2 seconds.

11. A musical instrument according to claim 8 in which the triggerable circuit is an integrator circuit.

12. A musical instrument according to claim 8 in which the triggerable circuit produces a ramp potential which increases linearly with time.

13. A musical instrument according to claim 8 which includes a reset circuit under the control of said arpeggio switch and connected to the triggerable circuit for terminating the potential increase and hence the arpeggio before said period of time has elapsed.

14. A musical instrument according to claim 8 including a current amplifier connected between the triggerable circuit and said cascade circuit.

15. A musical instrument according to claim 8 in which said cascade circuit comprises:

a. a series of normally charged capacitors connected to provide said pulses of gating potential in response to their being discharged;

b. a series of low-impedance discharge paths for said capacitors respectively including normally nonconducting pulse gates under the control of the triggerable circuit; and

c. means connected to said pulse gates and forming a part of said low-impedance discharge paths for rendering successive pulse gates progressively responsive to increasing control potentials.

16. A musical instrument according to claim in which said capacitors are connected at one side to the keying potential and at the other side to a higher potential through a high impedance.

1?. A musical instrument according to claim 15 in which saidrendering means includes diode means between successive ones of said pulse gates.

18. A musical instrument according to claim 17 in which said diode means is a pair of diodes connected in series.

19. A musical instrument according to claim 8 in which said cascade circuit comprises:

a. a capacitor in each stage arranged to be discharged through a low-impedance path and to be charged through a high-impedance path;

b. said low-impedance path including a normally nonconducting pulse gate in each stage, and means for providing a potential reference between adjacent stages;

c. said reference potential means being connected in series with each other;

d. each said pulse gate having a control terminal connected to receive the increasing potential from the triggerable circuit; and

e. connections between said stages and said series of control gates for transmitting said spaced pulses.

20. A musical instrument according to claim 8 in which the triggerable circuit includes an integrating transistor, and a capacitor connected between the base and the collector of said transistor.

21. A musical instrument according to claim 8 including a gate connected between the output of the triggerable circuit and ground, and connected to be rendered conductive in response to release of the arpeggio switch for instantly terminating any arpeggio.

22. A musical instrument according to claim 8 in which the triggerable circuit includes:

a. an integrating transistor connected between the source of keying potential and said cascade circuit;

b. a capacitor connected between the base and collector of said integrating transistor;

c. a control transistor connected between the source of keying potential and the base of said integrating transistor; and

d. the base of said control transistor being connected to said arpeggio switch.

23. A musical instrument according to claim 8 in which the triggerable circuit includes;

a. an integrating transistor connected between the source of keying potential and said cascade circuit;

b. a normally charged capacitor connected between the base and collector of said integrating transistor;

c. a normally conducting control transistor connected through a low-impedance path between the source of keying potential and a point between said capacitor and the base of said integrating transistor for charging said capacitor and for biasing said integrating transistor to be nonconductive;

d. the base of said control transistor being connected to said arpeggio switch; and

e. means providing a somewhat higher impedance path from said point to provide a discharge path for said capacitor; whereby closing of said arpeggio switch instantly biases said control transistor to be nonconductive, thereby enabling said capacitor to discharge at a rate determined by said higher impedance path, thereby progressively removing the bias from the integrating transistor to render it progressively more conductive during said discharge.

24. A musical instrument according to claim 23 in which said higher impedance path comprises an adjustable voltage divider.

25. A musical instrument according to claim 23 which includes a reset transistor connected in the charging path for said capacitor, the base of said reset transistor being normally biased to render the reset transistor conductive under the control of said arpeggio switch, whereby upon release of said arpeggio switch the normal bias on said reset transistor is instantly reestablished.

26. A musical instrument according to claim 1 in which said pulse applying means comprises an electrical circuit, responsive to each cycle of operation of said arpeggio switch, and including a series of sequentially operative stages for automatically providing said spaced pulses of gating potential. 

1. A musical instrument comprising: a. a series of tone producing means having frequencies corresponding to a chromatic musical scale; b. a keyboard having a left-hand portion and a right-hand portion, said keyboard including a series of keys connected to respective ones of said tone producing means to control the tone production; c. a set of key switches under the control of the keys of the left-hand portion of said keyboard connected for providing a keying potential; d. a series of control gates respectively interconnecting said key switches with musically corresponding ones of the tone producing means associated with the right-hand portion of said keyboard to control tone production independently of the directly associated keys; e. a selectably actuatable arpeggio switch connected for providing a potential; and f. means responsive to the potential from said arpeggio switch for successively applying spaced pulses of gating potential to said series of control gates.
 2. A musical instrument according to claim 1 in which a plurality of octavely related ones of said control gates are connected together to receive keying potential simultaneously from the corresponding key switch.
 3. A musical instrument according to claim 2 in which a plurality of octavely related ones of said key switches are connected together.
 4. A musical instrument according to claim 1 in which diodes are located in series between said key switches and said control gates.
 5. A musical instrument according to claim 1 in which said control gates are arranged in groups each including the control gates for controlling a plurality of chromatically adjacent ones of said tone producing means, the control gates of each group being connected together for receiving one of the pulses of the gating potential.
 6. A musical instrument according to claim 5 including means so interconnecting pairs of chromatically adjacent groups of control gates that the control gate of one group of one of the pairs of groups, which gate is chromatically the closest to the other group of the pair, will receive the successive gating pulses for both of such groups.
 7. A musical instrument according to claim 5 including means so interconnecting the control gate associated with the lowest frequency tone producing means of one group with the adjacent group associated with Lower frequency tone producing means that said control gate will also receive the gating pulse for said adjacent group.
 8. A musical instrument according to claim 1 in which said pulse applying means comprises: a. a circuit, connected to be triggered by each cycle of operation of said arpeggio switch, for providing a potential that increases for a period of time at least as great as the desired arpeggio duration; and b. a cascade circuit having a series of stages arranged to be progressively responsive to such potential increase to provide said spaced pulses of gating potential.
 9. A musical instrument according to claim 8 including means in the triggerable circuit for selectably adjusting said period of time.
 10. A musical instrument according to claim 9 in which said adjusting means has a range of about 2 seconds.
 11. A musical instrument according to claim 8 in which the triggerable circuit is an integrator circuit.
 12. A musical instrument according to claim 8 in which the triggerable circuit produces a ramp potential which increases linearly with time.
 13. A musical instrument according to claim 8 which includes a reset circuit under the control of said arpeggio switch and connected to the triggerable circuit for terminating the potential increase and hence the arpeggio before said period of time has elapsed.
 14. A musical instrument according to claim 8 including a current amplifier connected between the triggerable circuit and said cascade circuit.
 15. A musical instrument according to claim 8 in which said cascade circuit comprises: a. a series of normally charged capacitors connected to provide said pulses of gating potential in response to their being discharged; b. a series of low-impedance discharge paths for said capacitors respectively including normally nonconducting pulse gates under the control of the triggerable circuit; and c. means connected to said pulse gates and forming a part of said low-impedance discharge paths for rendering successive pulse gates progressively responsive to increasing control potentials.
 16. A musical instrument according to claim 15 in which said capacitors are connected at one side to the keying potential and at the other side to a higher potential through a high impedance.
 17. A musical instrument according to claim 15 in which said rendering means includes diode means between successive ones of said pulse gates.
 18. A musical instrument according to claim 17 in which said diode means is a pair of diodes connected in series.
 19. A musical instrument according to claim 8 in which said cascade circuit comprises: a. a capacitor in each stage arranged to be discharged through a low-impedance path and to be charged through a high-impedance path; b. said low-impedance path including a normally nonconducting pulse gate in each stage, and means for providing a potential reference between adjacent stages; c. said reference potential means being connected in series with each other; d. each said pulse gate having a control terminal connected to receive the increasing potential from the triggerable circuit; and e. connections between said stages and said series of control gates for transmitting said spaced pulses.
 20. A musical instrument according to claim 8 in which the triggerable circuit includes an integrating transistor, and a capacitor connected between the base and the collector of said transistor.
 21. A musical instrument according to claim 8 including a gate connected between the output of the triggerable circuit and ground, and connected to be rendered conductive in response to release of the arpeggio switch for instantly terminating any arpeggio.
 22. A musical instrument according to claim 8 in which the triggerable circuit includes: a. an integrating transistor connected between the source of keying potential and said cascade circuit; b. a capacitor connected between the base and collector of said integrating transistoR; c. a control transistor connected between the source of keying potential and the base of said integrating transistor; and d. the base of said control transistor being connected to said arpeggio switch.
 23. A musical instrument according to claim 8 in which the triggerable circuit includes; a. an integrating transistor connected between the source of keying potential and said cascade circuit; b. a normally charged capacitor connected between the base and collector of said integrating transistor; c. a normally conducting control transistor connected through a low-impedance path between the source of keying potential and a point between said capacitor and the base of said integrating transistor for charging said capacitor and for biasing said integrating transistor to be nonconductive; d. the base of said control transistor being connected to said arpeggio switch; and e. means providing a somewhat higher impedance path from said point to provide a discharge path for said capacitor; whereby closing of said arpeggio switch instantly biases said control transistor to be nonconductive, thereby enabling said capacitor to discharge at a rate determined by said higher impedance path, thereby progressively removing the bias from the integrating transistor to render it progressively more conductive during said discharge.
 24. A musical instrument according to claim 23 in which said higher impedance path comprises an adjustable voltage divider.
 25. A musical instrument according to claim 23 which includes a reset transistor connected in the charging path for said capacitor, the base of said reset transistor being normally biased to render the reset transistor conductive under the control of said arpeggio switch, whereby upon release of said arpeggio switch the normal bias on said reset transistor is instantly reestablished.
 26. A musical instrument according to claim 1 in which said pulse applying means comprises an electrical circuit, responsive to each cycle of operation of said arpeggio switch, and including a series of sequentially operative stages for automatically providing said spaced pulses of gating potential. 